Boisea rubrolineata
In 3 days ~30% in a week ~50%
Boisea rubrolineata or the western boxelder bug is identical to the eastern boxelder bug aside from having prominent red veins on its corium. It is found in western North America. Adults are 9–13 mm in length. The thorax and wings are black with red lines, and the abdomen is red. Nymphs are bright red and gray. Both nymphs and adults feed on boxelder. In fall and winter, adults might be noted migrating indoors to hibernate. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Yosemite National Park | 🇺🇸 United States | |
| 2 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Portland | 🇺🇸 United States | |
| 2 | Sacramento | 🇺🇸 United States | |
| 3 | San Francisco | 🇺🇸 United States | |
| 4 | Seattle | 🇺🇸 United States | |
| 5 | Los Angeles | 🇺🇸 United States | |
| 6 | San Diego | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Western Boxelder Bug sighting in Yosemite National Park on a given day, based on 33 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 51st most-seen of the 227 insects we can rate there. Over three days the chance rises to about 30%, and over a week to about 50%, if each day is a fresh chance.
February and March
In those months about 30% of wildlife watchers report a Western Boxelder Bug in Yosemite National Park on a given day, against under 5% in August to December, the lowest months. Those are among Yosemite National Park's wettest months, with about 180 mm of rain a month against 25 mm in September.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Western Boxelder Bug sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 2 parks where we can rate Western Boxelder Bug sightings, Yosemite National Park has the highest daily chance: about 10%. Next come Sequoia and Kings Canyon National Parks (United States, about 10%).
Same order: Hemiptera
The closest relatives of the Western Boxelder Bug that you can see in Yosemite National Park (order Hemiptera, True Bugs, Hoppers, Aphids, and allies) are North American Common Water Strider (about 10%), Small Milkweed Bug (about 10%) and Manzanita Leafgall Aphid (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Western Boxelder Bug is recorded against all the insects logged in Yosemite National Park (33 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
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